Change to set LWT only once

[zuckschwerdt]

This moves MQTT publishing of "online" to the /status topic from the regular publishMqtt() to onMqttConnect().

This way the LWT topic is only set on restart and after wifi or the MQTT connection was lost.

If you track the LWT topic then any change now indicates trouble (wifi lost, reboot, …).

Implementation details:

• onMqttConnect()s subuf increased by 3 chars as "/status" is 3 chars longer than "/col"/"/api". Although I think one char less would suffice.
• Publishing of /status is not done if USERMOD_SMARTNEST is defined, same as before this PR.
• Publishing of /status is after UsermodManager::onMqttConnect() hooks, same as before this PR. Although I think we could reasonably set it earlier.

Summary by CodeRabbit

• New Features
  • The device now publishes an "online" status message to the MQTT topic immediately after connecting.
• Bug Fixes
  • Prevented duplicate "online" status messages from being published to the MQTT topic.

[coderabbitai]

Walkthrough

The changes modify the MQTT status message handling in the code. The buffer size for MQTT topic strings was increased, and the logic for publishing the retained "online" status message was moved from the publishMqtt() function to the onMqttConnect() function, with a conditional compilation guard to exclude certain builds.

Changes

File(s)	Change Summary
wled00/mqtt.cpp	Increased buffer size for topic strings; moved retained "online" status message publishing to onMqttConnect() and removed it from publishMqtt(); added conditional compilation guard for the new logic.

Possibly related issues

• Set /status LWT topic only once #4696: The changes directly address the issue by moving the MQTT retained "online" status message publishing logic from publishMqtt() to onMqttConnect(), as discussed in the issue.

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Reviewing files that changed from the base of the PR and between 25223c4 and 817157b.

📒 Files selected for processing (1)

• wled00/mqtt.cpp (2 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (13)

• GitHub Check: wled_build / Build Environments (esp32dev_V4)
• GitHub Check: wled_build / Build Environments (esp32dev)
• GitHub Check: wled_build / Build Environments (esp32s3_4M_qspi)
• GitHub Check: wled_build / Build Environments (esp32_eth)
• GitHub Check: wled_build / Build Environments (esp01_1m_full_compat)
• GitHub Check: wled_build / Build Environments (usermods)
• GitHub Check: wled_build / Build Environments (esp32_wrover)
• GitHub Check: wled_build / Build Environments (esp32s3dev_8MB_opi)
• GitHub Check: wled_build / Build Environments (esp32s3dev_16MB_opi)
• GitHub Check: wled_build / Build Environments (lolin_s2_mini)
• GitHub Check: wled_build / Build Environments (esp32c3dev)
• GitHub Check: wled_build / Build Environments (esp8266_2m)
• GitHub Check: wled_build / Build Environments (esp8266_2m_compat)

🔇 Additional comments (2)

wled00/mqtt.cpp (2)

30-30: Buffer size increase is appropriate.

The buffer size increase from MQTT_MAX_TOPIC_LEN + 6 to MQTT_MAX_TOPIC_LEN + 9 accommodates the longer "/status" topic (7 chars) compared to the previously used "/col" or "/api" topics (4 chars). This change is necessary and correctly sized.

---

55-60: Well-placed relocation of status publishing.

Moving the "online" status publishing from publishMqtt() to onMqttConnect() is a good improvement. This ensures the LWT status is set only once upon connection, making it more accurate for tracking connection issues like Wi-Fi loss or device reboot.

The placement after the UsermodManager::onMqttConnect() call maintains the original execution order, and the #ifndef USERMOD_SMARTNEST guard is consistent with the rest of the codebase.

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[zuckschwerdt]

Resolves #4696

[blazoncek]

👍